An internal combustion engine mounted on a vehicle like an automobile performs cooling with a coolant to suppress an excessive temperature rise accompanying engine operation. The coolant circulates through circulation passages, thereby flowing through the interior of the internal combustion engine. When the coolant flows through the interior of the internal combustion engine, heat transfer takes place between the coolant and the internal combustion engine, and thus the internal combustion engine is cooled.
When an internal combustion engine is subjected to warm-up at the time of, for example, engine start-up, it is preferable to restrict the flow of the coolant through the interior of the internal combustion engine to complete the engine warm-up as early as possible. For example, Patent Document 1 discloses that the flow of the coolant through the interior of the internal combustion engine is restricted by deactivating a pump that circulates the coolant. When the flow of the coolant through the interior of the internal combustion engine is restricted during the engine warm-up, the warm-up is accelerated and can be completed early.
Moreover, Patent Document 1 discloses that while the flow of the coolant through the interior of the internal combustion engine is restricted, it is determined whether or not the warm-up of the internal combustion engine has completed based on the temperature of the coolant detected by a coolant temperature sensor, an accumulated value of the intake air amount by the internal combustion engine, and the accumulated value of the time during which the above-described restriction is performed. Furthermore, Patent Document 1 discloses that when it is determined that the warm-up has been completed through the above-described determination on whether or not the engine warm-up has completed, the flow restriction of the coolant through the interior of the internal combustion engine is canceled.